call method

@override String? call(String attribute, String value)

Validates whether a value matches a specified pattern (equality check).

This method checks if the input value is equal to the specified pattern. If the value is not equal to the pattern, an error message is generated using the buildMessage method.

Parameters:

• attribute: The identifier of the form attribute being validated.
• value: The value to be validated.

Returns: A validation error message if the value is not equal to the pattern, or null if the value is equal to the pattern.

Implementation

@override
String? call(String attribute, String value) {
  if (value.isNotEmpty) {
    if (value != pattern) {
      return buildMessage(attribute, value, onExtra: (message) {
        message.replaceAll(':pattern', pattern);
        return message;
      });
    }
  }
  return null;
}